Mtlmix can't mix 2 shader

[Brizengan]

I use Houdini and i can't mixed two shader. If i try to mix 2 texture color the node mtlxmix work fine. But if i use the matX mix to mix two shader he dont work

[jstone-lucasfilm]

@Brizengan, this sounds more like a question for the Houdini Solaris team! MaterialX definitely has the ability to perform a mix between two surface shaders, and we have an example of this usage in our test suite:

https://github.com/AcademySoftwareFoundation/MaterialX/blob/main/resources/Materials/TestSuite/pbrlib/surfaceshader/shader_ops.mtlx

Is there a forum for Houdini Solaris where you could bring this up, and experts on their team could provide advice on this usage?

[Brizengan]

Hmm, The only way is to report a bug to Sidefx. We can talk about it in the forum but I don't think the devs are there. In any case, this problem puts a big brake on the production speed :/

[jstone-lucasfilm]

Here's another good example of surface shader mixing in MaterialX, and you can load this example directly in MaterialXView, to visualize what happens as you adjust the mix weight:

https://github.com/AcademySoftwareFoundation/MaterialX/blob/main/resources/Materials/TestSuite/pbrlib/surfaceshader/surface_ops.mtlx

Here are some screenshots of this mix node in action, blending between two very different surface shaders in MaterialXView:

Mix weight 0.0:

Mix weight 0.5:

Mix weight 1.0:

My sense is that this feature is working as expected in the open-source MaterialX codebase, and the next step would be to follow up with the Houdini/Solaris team, as they have developed some very sophisticated closed-source code for MaterialX handling in Solaris, which our team does not have access to.

[jstone-lucasfilm]

@Brizengan I'll close out this issue for now, but feel free to reopen if the related SideFX discussions point out improvements we can make in the open-source codebase.